1. Field of the Invention
The present invention relates to a technology for agitating toner in a toner hopper of an image forming apparatus.
2. Description of the Related Art
A typical developing unit of an image forming apparatus includes a toner hopper that houses developing toner. The toner hopper incorporates a toner agitating unit that agitates toner that is to be supplied to a developing roller so that toner is uniformly and constantly supplied to the developing roller.
A toner agitating unit is disclosed in Japanese Patent Application Laid-open No. 2001-318517. This agitating unit includes a flexible agitating member attached to a rotary shaft. To improve agitation efficiency, the agitating member has a shape that causes the agitating member to experience a high drag from toner during agitation. More specifically, the agitating member has the shape of a flat plate (see FIG. 2 of Japanese Patent Application Laid-open No. 2001-318517).
However, because the agitating member has the shape of a flat plate, toner flows from a center portion of the agitating member toward its end portions when the agitating unit agitates the toner so that stress is likely to concentrate on the end portions of the agitating member. Such stress concentration may result in local plastic deformation of the agitating member, and repeated stress may cause damage to the agitating member.